pub struct LineWriter<W> where
W: Write, { /* private fields */ }
Expand description
Wraps a writer and buffers output to it, flushing whenever a newline
(0x0a
, '\n'
) is detected.
The BufWriter
struct wraps a writer and buffers its output.
But it only does this batched write when it goes out of scope, or when the
internal buffer is full. Sometimes, you’d prefer to write each line as it’s
completed, rather than the entire buffer at once. Enter LineWriter
. It
does exactly that.
Like BufWriter
, a LineWriter
’s buffer will also be flushed when the
LineWriter
goes out of scope or when its internal buffer is full.
If there’s still a partial line in the buffer when the LineWriter
is
dropped, it will flush those contents.
Examples
We can use LineWriter
to write one line at a time, significantly
reducing the number of actual writes to the file.
use std::fs::{self, File};
use std::io::prelude::*;
use std::io::LineWriter;
fn main() -> std::io::Result<()> {
let road_not_taken = b"I shall be telling this with a sigh
Somewhere ages and ages hence:
Two roads diverged in a wood, and I -
I took the one less traveled by,
And that has made all the difference.";
let file = File::create("poem.txt")?;
let mut file = LineWriter::new(file);
file.write_all(b"I shall be telling this with a sigh")?;
// No bytes are written until a newline is encountered (or
// the internal buffer is filled).
assert_eq!(fs::read_to_string("poem.txt")?, "");
file.write_all(b"\n")?;
assert_eq!(
fs::read_to_string("poem.txt")?,
"I shall be telling this with a sigh\n",
);
// Write the rest of the poem.
file.write_all(b"Somewhere ages and ages hence:
Two roads diverged in a wood, and I -
I took the one less traveled by,
And that has made all the difference.")?;
// The last line of the poem doesn't end in a newline, so
// we have to flush or drop the `LineWriter` to finish
// writing.
file.flush()?;
// Confirm the whole poem was written.
assert_eq!(fs::read("poem.txt")?, &road_not_taken[..]);
Ok(())
}
Implementations
sourceimpl<W> LineWriter<W> where
W: Write,
impl<W> LineWriter<W> where
W: Write,
sourcepub fn new(inner: W) -> LineWriter<W>ⓘNotable traits for LineWriter<W>impl<W> Write for LineWriter<W> where
W: Write,
pub fn new(inner: W) -> LineWriter<W>ⓘNotable traits for LineWriter<W>impl<W> Write for LineWriter<W> where
W: Write,
W: Write,
Creates a new LineWriter
.
Examples
use std::fs::File;
use std::io::LineWriter;
fn main() -> std::io::Result<()> {
let file = File::create("poem.txt")?;
let file = LineWriter::new(file);
Ok(())
}
sourcepub fn with_capacity(capacity: usize, inner: W) -> LineWriter<W>ⓘNotable traits for LineWriter<W>impl<W> Write for LineWriter<W> where
W: Write,
pub fn with_capacity(capacity: usize, inner: W) -> LineWriter<W>ⓘNotable traits for LineWriter<W>impl<W> Write for LineWriter<W> where
W: Write,
W: Write,
Creates a new LineWriter
with at least the specified capacity for the
internal buffer.
Examples
use std::fs::File;
use std::io::LineWriter;
fn main() -> std::io::Result<()> {
let file = File::create("poem.txt")?;
let file = LineWriter::with_capacity(100, file);
Ok(())
}
sourcepub fn get_ref(&self) -> &W
pub fn get_ref(&self) -> &W
Gets a reference to the underlying writer.
Examples
use std::fs::File;
use std::io::LineWriter;
fn main() -> std::io::Result<()> {
let file = File::create("poem.txt")?;
let file = LineWriter::new(file);
let reference = file.get_ref();
Ok(())
}
sourcepub fn get_mut(&mut self) -> &mut W
pub fn get_mut(&mut self) -> &mut W
Gets a mutable reference to the underlying writer.
Caution must be taken when calling methods on the mutable reference returned as extra writes could corrupt the output stream.
Examples
use std::fs::File;
use std::io::LineWriter;
fn main() -> std::io::Result<()> {
let file = File::create("poem.txt")?;
let mut file = LineWriter::new(file);
// we can use reference just like file
let reference = file.get_mut();
Ok(())
}
sourcepub fn into_inner(self) -> Result<W, IntoInnerError<LineWriter<W>>>
pub fn into_inner(self) -> Result<W, IntoInnerError<LineWriter<W>>>
Unwraps this LineWriter
, returning the underlying writer.
The internal buffer is written out before returning the writer.
Errors
An Err
will be returned if an error occurs while flushing the buffer.
Examples
use std::fs::File;
use std::io::LineWriter;
fn main() -> std::io::Result<()> {
let file = File::create("poem.txt")?;
let writer: LineWriter<File> = LineWriter::new(file);
let file: File = writer.into_inner()?;
Ok(())
}
Trait Implementations
sourceimpl<W> Debug for LineWriter<W> where
W: Write + Debug,
impl<W> Debug for LineWriter<W> where
W: Write + Debug,
sourceimpl<W> Write for LineWriter<W> where
W: Write,
impl<W> Write for LineWriter<W> where
W: Write,
sourcefn write(&mut self, buf: &[u8]) -> Result<usize, Error>
fn write(&mut self, buf: &[u8]) -> Result<usize, Error>
Write a buffer into this writer, returning how many bytes were written. Read more
sourcefn flush(&mut self) -> Result<(), Error>
fn flush(&mut self) -> Result<(), Error>
Flush this output stream, ensuring that all intermediately buffered contents reach their destination. Read more
sourcefn is_write_vectored(&self) -> bool
fn is_write_vectored(&self) -> bool
can_vector
)Determines if this Write
r has an efficient write_vectored
implementation. Read more
sourcefn write_all(&mut self, buf: &[u8]) -> Result<(), Error>
fn write_all(&mut self, buf: &[u8]) -> Result<(), Error>
Attempts to write an entire buffer into this writer. Read more
sourcefn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> Result<(), Error>
fn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> Result<(), Error>
write_all_vectored
)Attempts to write multiple buffers into this writer. Read more
Auto Trait Implementations
impl<W> RefUnwindSafe for LineWriter<W> where
W: RefUnwindSafe,
impl<W> Send for LineWriter<W> where
W: Send,
impl<W> Sync for LineWriter<W> where
W: Sync,
impl<W> Unpin for LineWriter<W> where
W: Unpin,
impl<W> UnwindSafe for LineWriter<W> where
W: UnwindSafe,
Blanket Implementations
sourceimpl<T> BorrowMut<T> for T where
T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
const: unstable · sourcefn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more
sourceimpl<T> Downcast for T where
T: Any,
impl<T> Downcast for T where
T: Any,
sourcefn into_any(self: Box<T, Global>) -> Box<dyn Any + 'static, Global>ⓘNotable traits for Box<W, Global>impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<R> Read for Box<R, Global> where
R: Read + ?Sized, impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;
fn into_any(self: Box<T, Global>) -> Box<dyn Any + 'static, Global>ⓘNotable traits for Box<W, Global>impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<R> Read for Box<R, Global> where
R: Read + ?Sized, impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;
W: Write + ?Sized, impl<R> Read for Box<R, Global> where
R: Read + ?Sized, impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;
Convert Box<dyn Trait>
(where Trait: Downcast
) to Box<dyn Any>
. Box<dyn Any>
can
then be further downcast
into Box<ConcreteType>
where ConcreteType
implements Trait
. Read more
sourcefn into_any_rc(self: Rc<T>) -> Rc<dyn Any + 'static>
fn into_any_rc(self: Rc<T>) -> Rc<dyn Any + 'static>
Convert Rc<Trait>
(where Trait: Downcast
) to Rc<Any>
. Rc<Any>
can then be
further downcast
into Rc<ConcreteType>
where ConcreteType
implements Trait
. Read more
sourcefn as_any(&self) -> &(dyn Any + 'static)
fn as_any(&self) -> &(dyn Any + 'static)
Convert &Trait
(where Trait: Downcast
) to &Any
. This is needed since Rust cannot
generate &Any
’s vtable from &Trait
’s. Read more
sourcefn as_any_mut(&mut self) -> &mut (dyn Any + 'static)
fn as_any_mut(&mut self) -> &mut (dyn Any + 'static)
Convert &mut Trait
(where Trait: Downcast
) to &Any
. This is needed since Rust cannot
generate &mut Any
’s vtable from &mut Trait
’s. Read more
sourceimpl<T> DowncastSync for T where
T: Any + Send + Sync,
impl<T> DowncastSync for T where
T: Any + Send + Sync,
sourceimpl<A> DynCastExt for A
impl<A> DynCastExt for A
sourcefn dyn_cast<T>(
self
) -> Result<<A as DynCastExtHelper<T>>::Target, <A as DynCastExtHelper<T>>::Source> where
A: DynCastExtHelper<T>,
T: ?Sized,
fn dyn_cast<T>(
self
) -> Result<<A as DynCastExtHelper<T>>::Target, <A as DynCastExtHelper<T>>::Source> where
A: DynCastExtHelper<T>,
T: ?Sized,
Use this to cast from one trait object type to another. Read more
sourcefn dyn_upcast<T>(self) -> <A as DynCastExtAdvHelper<T, T>>::Target where
A: DynCastExtAdvHelper<T, T, Source = <A as DynCastExtAdvHelper<T, T>>::Target>,
T: ?Sized,
fn dyn_upcast<T>(self) -> <A as DynCastExtAdvHelper<T, T>>::Target where
A: DynCastExtAdvHelper<T, T, Source = <A as DynCastExtAdvHelper<T, T>>::Target>,
T: ?Sized,
Use this to upcast a trait to one of its supertraits. Read more
sourcefn dyn_cast_adv<F, T>(
self
) -> Result<<A as DynCastExtAdvHelper<F, T>>::Target, <A as DynCastExtAdvHelper<F, T>>::Source> where
A: DynCastExtAdvHelper<F, T>,
F: ?Sized,
T: ?Sized,
fn dyn_cast_adv<F, T>(
self
) -> Result<<A as DynCastExtAdvHelper<F, T>>::Target, <A as DynCastExtAdvHelper<F, T>>::Source> where
A: DynCastExtAdvHelper<F, T>,
F: ?Sized,
T: ?Sized,
sourcefn dyn_cast_with_config<C>(
self
) -> Result<<A as DynCastExtAdvHelper<<C as DynCastConfig>::Source, <C as DynCastConfig>::Target>>::Target, <A as DynCastExtAdvHelper<<C as DynCastConfig>::Source, <C as DynCastConfig>::Target>>::Source> where
C: DynCastConfig,
A: DynCastExtAdvHelper<<C as DynCastConfig>::Source, <C as DynCastConfig>::Target>,
fn dyn_cast_with_config<C>(
self
) -> Result<<A as DynCastExtAdvHelper<<C as DynCastConfig>::Source, <C as DynCastConfig>::Target>>::Target, <A as DynCastExtAdvHelper<<C as DynCastConfig>::Source, <C as DynCastConfig>::Target>>::Source> where
C: DynCastConfig,
A: DynCastExtAdvHelper<<C as DynCastConfig>::Source, <C as DynCastConfig>::Target>,
Use this to cast from one trait object type to another. With this method the type parameter is a config type that uniquely specifies which cast should be preformed. Read more
impl<T> RmpWrite for T where
T: Write,
impl<T> RmpWrite for T where
T: Write,
impl<V, T> VZip<V> for T where
V: MultiLane<T>,
impl<V, T> VZip<V> for T where
V: MultiLane<T>,
fn vzip(self) -> V
impl<W> WriteBytesExt for W where
W: Write + ?Sized,
impl<W> WriteBytesExt for W where
W: Write + ?Sized,
fn write_u8(&mut self, n: u8) -> Result<(), Error>
fn write_u8(&mut self, n: u8) -> Result<(), Error>
Writes an unsigned 8 bit integer to the underlying writer. Read more
fn write_i8(&mut self, n: i8) -> Result<(), Error>
fn write_i8(&mut self, n: i8) -> Result<(), Error>
Writes a signed 8 bit integer to the underlying writer. Read more
fn write_u16<T>(&mut self, n: u16) -> Result<(), Error> where
T: ByteOrder,
fn write_u16<T>(&mut self, n: u16) -> Result<(), Error> where
T: ByteOrder,
Writes an unsigned 16 bit integer to the underlying writer. Read more
fn write_i16<T>(&mut self, n: i16) -> Result<(), Error> where
T: ByteOrder,
fn write_i16<T>(&mut self, n: i16) -> Result<(), Error> where
T: ByteOrder,
Writes a signed 16 bit integer to the underlying writer. Read more
fn write_u24<T>(&mut self, n: u32) -> Result<(), Error> where
T: ByteOrder,
fn write_u24<T>(&mut self, n: u32) -> Result<(), Error> where
T: ByteOrder,
Writes an unsigned 24 bit integer to the underlying writer. Read more
fn write_i24<T>(&mut self, n: i32) -> Result<(), Error> where
T: ByteOrder,
fn write_i24<T>(&mut self, n: i32) -> Result<(), Error> where
T: ByteOrder,
Writes a signed 24 bit integer to the underlying writer. Read more
fn write_u32<T>(&mut self, n: u32) -> Result<(), Error> where
T: ByteOrder,
fn write_u32<T>(&mut self, n: u32) -> Result<(), Error> where
T: ByteOrder,
Writes an unsigned 32 bit integer to the underlying writer. Read more
fn write_i32<T>(&mut self, n: i32) -> Result<(), Error> where
T: ByteOrder,
fn write_i32<T>(&mut self, n: i32) -> Result<(), Error> where
T: ByteOrder,
Writes a signed 32 bit integer to the underlying writer. Read more
fn write_u48<T>(&mut self, n: u64) -> Result<(), Error> where
T: ByteOrder,
fn write_u48<T>(&mut self, n: u64) -> Result<(), Error> where
T: ByteOrder,
Writes an unsigned 48 bit integer to the underlying writer. Read more
fn write_i48<T>(&mut self, n: i64) -> Result<(), Error> where
T: ByteOrder,
fn write_i48<T>(&mut self, n: i64) -> Result<(), Error> where
T: ByteOrder,
Writes a signed 48 bit integer to the underlying writer. Read more
fn write_u64<T>(&mut self, n: u64) -> Result<(), Error> where
T: ByteOrder,
fn write_u64<T>(&mut self, n: u64) -> Result<(), Error> where
T: ByteOrder,
Writes an unsigned 64 bit integer to the underlying writer. Read more
fn write_i64<T>(&mut self, n: i64) -> Result<(), Error> where
T: ByteOrder,
fn write_i64<T>(&mut self, n: i64) -> Result<(), Error> where
T: ByteOrder,
Writes a signed 64 bit integer to the underlying writer. Read more
fn write_u128<T>(&mut self, n: u128) -> Result<(), Error> where
T: ByteOrder,
fn write_u128<T>(&mut self, n: u128) -> Result<(), Error> where
T: ByteOrder,
Writes an unsigned 128 bit integer to the underlying writer.
fn write_i128<T>(&mut self, n: i128) -> Result<(), Error> where
T: ByteOrder,
fn write_i128<T>(&mut self, n: i128) -> Result<(), Error> where
T: ByteOrder,
Writes a signed 128 bit integer to the underlying writer.
fn write_uint<T>(&mut self, n: u64, nbytes: usize) -> Result<(), Error> where
T: ByteOrder,
fn write_uint<T>(&mut self, n: u64, nbytes: usize) -> Result<(), Error> where
T: ByteOrder,
Writes an unsigned n-bytes integer to the underlying writer. Read more
fn write_int<T>(&mut self, n: i64, nbytes: usize) -> Result<(), Error> where
T: ByteOrder,
fn write_int<T>(&mut self, n: i64, nbytes: usize) -> Result<(), Error> where
T: ByteOrder,
Writes a signed n-bytes integer to the underlying writer. Read more
fn write_uint128<T>(&mut self, n: u128, nbytes: usize) -> Result<(), Error> where
T: ByteOrder,
fn write_uint128<T>(&mut self, n: u128, nbytes: usize) -> Result<(), Error> where
T: ByteOrder,
Writes an unsigned n-bytes integer to the underlying writer. Read more
fn write_int128<T>(&mut self, n: i128, nbytes: usize) -> Result<(), Error> where
T: ByteOrder,
fn write_int128<T>(&mut self, n: i128, nbytes: usize) -> Result<(), Error> where
T: ByteOrder,
Writes a signed n-bytes integer to the underlying writer. Read more